Memory device

Abstract

According to one embodiment, a memory device includes a first electrode, a second electrode and a resistance change film. The resistance change film is connected between the first electrode and the second electrode. An ion metal is introduced in a matrix material in the resistance change film. A concentration of the ion metal in a first region on the first electrode side of the resistance change film is higher than a concentration of the ion metal in a second region on the second electrode side of the resistance change film A layer made of only the ion metal is not provided in the memory device.

What is claimed is: 
     
       1. A memory device comprising:
 a first electrode; 
 a second electrode; and 
 a resistance change film connected between the first electrode and the second electrode, 
 wherein: 
 an ion metal is introduced in a matrix material in the resistance change film, 
 a concentration of the ion metal in a first region on the first electrode side of the resistance change film is higher than a concentration of the ion metal in a second region on the second electrode side of the resistance change film, and 
 the memory device does not include a layer which supplies the resistance change film with ions. 
 
     
     
       2. The device according to  claim 1 , wherein:
 the first region is a region extending at a distance of two thirds or less of a film thickness of the resistance change film from a surface on the first electrode side of the resistance change film, and 
 the second region is a region extending at a distance of one third or less of a film thickness of the resistance change film from a surface on the second electrode side of the resistance change film. 
 
     
     
       3. The device according to  claim 1 , wherein a resistivity of the second region is 8×10 4  (Ω·m) or more. 
     
     
       4. The device according to  claim 1 , wherein:
 the matrix material is amorphous silicon, 
 the ion metal is silver, and 
 a concentration of the ion metal in the second region is 1×10 21  (atoms/cm 3 ) or less. 
 
     
     
       5. The device according to  claim 4 , wherein a concentration of the ion metal in the first region is not less than 1×10 18  (atoms/cm 3 ) and not more than 2×10 22  (atoms/cm 3 ). 
     
     
       6. The device according to  claim 1 , wherein the resistance change film comprises a multilayer film in which a plurality of layers are stacked, the plurality of layers having different matrix materials from one another. 
     
     
       7. The device according to  claim 6 , wherein the resistance change film includes:
 a first layer disposed on the first electrode side, the matrix material of the first layer being amorphous silicon or polysilicon; and 
 a second layer disposed on the second electrode side, the matrix material of the second layer being silicon oxide, silicon nitride, or silicon oxynitride. 
 
     
     
       8. The device according to  claim 6 , wherein the resistance change film includes:
 a first layer disposed on the first electrode side, the matrix material of the first layer being silicon oxide, silicon nitride, or silicon oxynitride; and 
 a second layer disposed on the second electrode side, the matrix material of the second layer being amorphous silicon or polysilicon. 
 
     
     
       9. The device according to  claim 1 , wherein a film thickness of the resistance change film is not less than 1 nm and not more than 100 nm. 
     
     
       10. The device according to  claim 1 , wherein:
 a voltage using the first electrode as a positive pole and the second electrode as a negative pole is applied to form a metal filament in the second region when the resistance change film transitions from a high resistance state to a low resistance state, and 
 a voltage using the first electrode as a negative pole and the second electrode as a positive pole is applied to eliminate at least part of the metal filament when the resistance change film transitions from a low resistance state to a high resistance state. 
 
     
     
       11. The device according to  claim 1 , wherein the matrix material is one or more materials selected from the group consisting of silicon, silicon oxide, silicon nitride, silicon oxynitride, silicon sulfide, silicon chloride, hafnium oxide, hafnium nitride, a hafnium silicate compound, zirconium oxide, zirconium nitride, a zirconium silicate compound, aluminum oxide, aluminum nitride, an aluminum silicate compound, titanium oxide, titanium nitride, and a titanium silicate compound. 
     
     
       12. The device according to  claim 1 , wherein the ion metal is one more metals selected from the group consisting of gold, silver, copper, platinum, palladium, titanium, iron, chromium, cobalt, nickel, aluminum, indium, tellurium, sodium, and calcium. 
     
     
       13. A memory device comprising:
 a first electrode; 
 a second electrode; and 
 a resistance change film connected between the first electrode and the second electrode and having a film thickness of not less than 1 nm and not more than 100 nm, 
 wherein: 
 silver is introduced in amorphous silicon in the resistance change film, 
 a concentration of silver in a first region is higher than a concentration of silver in a second region, the first region extending at a distance of two thirds or less of a film thickness of the resistance change film from a surface on the first electrode side of the resistance change film, and the second region extending at a distance of one third or less of a film thickness of the resistance change film from a surface on the second electrode side of the resistance change film, 
 the concentration of silver in the first region is not less than 1×10 18  (atoms/cm 3 ) and not more than 2×10 22  (atoms/cm 3 ), 
 the concentration of silver in the second region is 1×10 21  (atoms/cm 3 ) or less, 
 a resistivity of the second region is 8×10 4  (Ω·m) or more, 
 a voltage using the first electrode as a positive pole and the second electrode as a negative pole is applied to form a metal filament in the second region when the resistance change film transitions from a high resistance state to a low resistance state, 
 a voltage using the first electrode as a negative pole and the second electrode as a positive pole is applied to eliminate at least part of the metal filament when the resistance change film transitions from a low resistance state to a high resistance state, and 
 a layer made of only silver is not provided in the memory device.